Strange problem Tankar 2GM20

[Pär1]

Hello
On my sailing yacht the oilpressure lamp now is on with the key off. Key on the lamp goes off, no alarm in either case. The loading lamp acts as it should and the alternator give load.
I have not found any loose connections etc.
Any ideas?
Thanks, Pär

 

[Pär1]

Sorry, the spelling in my android fooled me, it should say Yanmar in the headline.
Pär